Atmospheric pressure (hot) plasmas caused by a DC arc have been known since the dawn of man. A common example is lightning. An industrial application of a DC arc plasma is a plasma gun, which is used in various manufacturing environments for forming coatings (typically ceramic materials).
Low pressure, glow discharge type (cold) plasma processes have been known for over a hundred years. As a matter of fact, most of current microelectronic material processing techniques use some form of low pressure plasma as their working environment.
In contrast, the present source provides a glow discharge atmospheric pressure (cold) plasma. Laboratory examples of such systems can be found in the literature: (1) Hideomi Koinuma et al "Development and application of a microbeam plasma generator" in Applied Physics Letters, Vol. 60, p. 816-817, Feb. 17, 1992; and, (2) Kiyoto Inomata et al "Open air deposition of SiO.sub.2 film from a cold plasma torch of tetramethoxysilane-H.sub.2 --Ar system" in Applied Physics Letters, Vol. 64, p. 46-48, January 1994. In the above referenced cases, the plasma is obtained by a continuous capacitive discharge at high voltage. Due to the small capacitance and very high impedance of the discharge tube, matching the load to a power supply with a typical matching network is difficult to realize. The conditions for enabling the production of a glow discharge plasma described in these papers are forced and to some degree, undesirable. To achieve a glow discharge a cabling configuration was designed which utilized a commercially available tuning network and boosted up power without very efficient power coupling.
The patent literature includes: U.S. Pat. No. 5,079,482 to Villeco et al. which discloses an electron beam discharge device which has an LC circuit formed by the secondary coil 30S of the Tesla coil 30 and the distributed capacitance 40A. This LC combination is located at the electron discharge gun 24.
U.S. Pat. No. 4,442,013 to Turchi et al. discloses a cold plasma-gun which has inductors 35, 50, 64 and capacitors 56, 30, 70 at the beam discharge.
U.S. Pat. No. 5,216,330 to Ahonen discloses an ion beam gun which discharges a cold plasma and which has an inductor 230 and capacitor 324 (see FIG. 4) at the beam discharge.
U.S. Pat. No. 5,285,046 to Hansz discloses an ion deposition source which has a pair of LC circuits (16a, 20a; 16b, 20b; see FIG. 4) driving the plasma discharge.
U.S. Pat. No. 4,931,700 to Reed discloses an electron beam gun which has an LC resonator (see FIG. 1) formed by inductor 7S and capacitor 5 driving the electron gun 10.
U.S. Pat. No. 4,849,675 to Mull discloses an ion beam gun which discharges a cold plasma and which has an inductor 2 and capacitor 15 (see FIG. 2) at the beam discharge; and,
U.S. Pat. No. 4,629,940 to Gagne et al. discloses a cold plasma generating torch which has an LC resonator formed by an inductor 28 and capacitors 66, 70 driving the discharge.